fix broken delay aggregation for alpha > 1

dht/dht.py

@@ -51,12 +51,6 @@ def lookup_for_hash(self, key: Hash):
             'aggrDelay': 0,
         }
 
-        closestnodes = self.rt.get_closest_nodes_to(key)
-        nodestotry = closestnodes.copy()
-        triednodes = deque()
-        lookupvalue = ""  # TODO: hardcoded to string
-        stepscnt = 0
-        concurrency = 0
         def has_closer_nodes(prev, new):
             for n, dist in new.items():
                 if n in prev:
@@ -68,9 +62,17 @@ def has_closer_nodes(prev, new):
                         continue
             return False
 
+        closestnodes = self.rt.get_closest_nodes_to(key)
+        nodestotry = closestnodes.copy()
+        triednodes = deque()
+        lookupvalue = ""  # TODO: hardcoded to string
+        stepscnt = 0
+
         while (stepscnt < self.lookupsteptostop) and (len(nodestotry) > 0):
             # ask queued nodes to try
             nodes = nodestotry.copy()
+            aggregateddelay = 0
+            concurrency = 0
             for node in nodes:
                 nodestotry.pop(node)  # remove item from peers to attempt
                 if node in triednodes:  # make sure we don't contact the same node twice
@@ -79,11 +81,12 @@ def has_closer_nodes(prev, new):
                 lookupsummary['connectionAttempts'] += 1
                 try:
                     connection, conndelay = self.network.connect_to_node(self.ID, node)
-                    lookupsummary['aggrDelay'] += conndelay
                     newnodes, val, ok, closestdelay = connection.get_closest_nodes_to(key)
                     if ok:
                         lookupvalue = val
-                    lookupsummary['aggrDelay'] += closestdelay
+                    operationdelay = conndelay + closestdelay
+                    if operationdelay > aggregateddelay:
+                        aggregateddelay = operationdelay
                     lookupsummary['successfulCons'] += 1
                     if has_closer_nodes(closestnodes, newnodes):
                         stepscnt = 0
@@ -93,10 +96,17 @@ def has_closer_nodes(prev, new):
                     else: 
                         stepscnt += 1
                 except ConnectionError:
+                    # count the delay of the connection attempt
+                    # TODO: take into account fast vs slow errors (https://github.com/cortze/py-dht/issues/14)
+                    if self.network.delayrange is not None:
+                        connErrorDelay = random.sample(self.network.delayrange, 1)[0]
+                        if connErrorDelay > aggregateddelay:
+                            aggregateddelay = connErrorDelay
                     lookupsummary['failedCons'] += 1
                     stepscnt += 1
                 concurrency += 1 
-                if concurrency >= self.alpha or stepscnt:
+                if concurrency >= self.alpha or stepscnt >= self.lookupsteptostop:
+                    lookupsummary['aggrDelay'] += aggregateddelay
                     break
 
         # finish with the summary

tests/test_network.py

@@ -145,7 +145,7 @@ def test_network_initialization(self):
     def test_dht_interop(self): 
         """ test if the nodes in the network actually route to the closest peer, and implicidly, if the DHTclient interface works """ 
         k = 10
-        size = 500 
+        size = 500
         id = 0
         errorrate = 0 # apply an error rate of 0 (to check if the logic pases)
         delayrange = None  # ms
@@ -306,6 +306,42 @@ def test_aggregated_delays(self):
         self.assertGreater(aggrdelay, bestdelay)
         self.assertLess(aggrdelay, worstdelay)
 
+    def test_aggregated_delays_and_alpha(self):
+        """ test if the interaction between the nodes in the network actually generate a compounded delay """
+        size = 500
+        i = 0
+        k = 10
+        jobs = 2
+        alpha = 3
+        beta = k
+        stepstostop = 3
+        errorrate = 0  # apply an error rate of 0 (to check if the logic pases)
+
+        delay = 50  # ms
+        delayrange = [delay, delay]  # ms
+
+        # init the network
+        n = DHTNetwork(i, errorrate, delayrange)
+        _ = n.init_with_random_peers(jobs, size, k, alpha, beta, stepstostop)
+
+        # use random node as lookup point
+        publishernodeid = random.sample(range(1, size), 1)[0]
+        pnode = n.nodestore.get_node(publishernodeid)
+        self.assertNotEqual(pnode.network.len(), 0)
+
+        # lookup
+        randomSegment = "my rollup sample"
+        segH = Hash(randomSegment)
+        interestednodeid = random.sample(range(1, size), 1)[0]
+        inode = n.nodestore.get_node(interestednodeid)
+        closestnodes, _, summary, aggrdelay = inode.lookup_for_hash(segH)
+        self.assertEqual(len(closestnodes), k)
+        lookuppeers = summary['connectionAttempts']
+        rounds = int(lookuppeers / alpha)
+        if (lookuppeers % alpha) > 0:
+            rounds += 1
+        self.assertEqual(aggrdelay, rounds * (delay*2))
+
 def generate_network(k, size, id, errorrate, delayrate):
     network = DHTNetwork(id, errorrate, delayrate)
     nodeids = range(0, size, 1)